A three-judge federal court panel in Chicago has opened the door for Republicans to try to learn the extent of the role played by the national Democratic Congressional Campaign Committee in the design of a new map of U.S. House districts in Illinois.

An order issued by U.S. District Judges Daniel Tinder, Robert Miller and Joan Lefkow allows lawyers representing a Republican-backed lawsuit trying to overturn the map to find out the identities of experts and consultants Illinois Democrats used to assist in drafting the state’s new congressional map.

Democrats, who control the Illinois legislature and governor’s office, approved new boundary lines for the state’s congressional districts in the once-every-decade procedure known as reapportionment. Ostensibly a process to try to equalize population in each district based on federal census results, redistricting also is a power game played by the political party that controls the mapmaking.

The political leanings of voters under the new map lines could reverse the partisan makeup of the state’s delegation, which turned 11-8 Republican during last year’s mid-term elections. Illinois will lose one U.S. House seat because its population did not increase as fast as other states and Democrats benefiting from the new map could pick up several seats now held by the GOP.

A group that includes all but one of the state’s current Republican congressmen challenged the Democratic map in July, contending it failed to adequately represent a growing Latino population and that it wrongly gerrymandered districts to dilute Republican representation. Democrats have argued that the map was fair and competitive.

Last month, Republicans asked the federal court panel to order Democrats to comply with several subpoenas about how the map was put together. In a ruling issued earlier this week, the three-judge panel said lawmakers and their staff had immunity from providing documents to Republicans that were not based on objective facts used to draw the new map.

But the panel said Democrats had to disclose to Republicans the identities of non-lawmakers who participated in decisions regarding the new map.

Republicans have maintained that the Democratic Congressional Campaign Committee played the pre-eminent role in drawing up new congressional districts for Illinois.

The GOP has alleged in court documents that one unnamed Republican member of the congressional delegation was informed by an unnamed Democratic member that the DCCC or one of its agents created a draft map that was incorporated almost wholesale into the map adopted by the legislature.

Democratic state lawmakers in Springfield also privately have said that the DCCC had been assisting in the redrawing of congressional boundaries.

Illinois Republicans also have a separate federal court case in Washington trying to get information from the DCCC about the state’s congressional map. A hearing is scheduled later this month.